In polishing of a semiconductor wafer, determination of a polishing endpoints at which polishing is performed can be known based on the criteria of the empirically obtained time. However, there are a variety of materials constituting the surface to be polished, and polishing times are all different depending upon the materials. In addition, materials constituting the surface to be polished are considered to change variously in future. Further, this is the same in the case of slurries and polishing apparatuses used for polishing. For this reason, it is so inefficient to obtain all polishing times in a variety of different polishing. On the other hand, recently, the optical endpoints detecting apparatus and method using an optical method which can directly measure the state of the surface to be polished have been studied, for example, as in JP-A-9-7985, JP-A-2000-326220 and the like.
In this optical endpoints detection apparatus and method, generally, a window not having essential ability such as absorption and transportation of slurry particles, which is composed of a hard uniform resin, through which the light for detecting an endpoints can transmit, is formed into a polishing pad, and the surface to be polished is observed only through this window, as disclosed in JP-A-11-512977 and the like.
However, since the window in the above-mentioned polishing pad has substantially no ability to retain and discharge the slurry, there is a possibility that provision of a window decreases the polishing ability of a polishing pad, and leads nonuniformity. In addition, for this reason, it is difficult to enlarge the window (provision in an annular manner and the like) and increase the number of the windows.